The use of corresponding layer systems has been proposed in particular for measurement transducers, magneto couplers or current sensors. A layer system of this type includes, as an important constituent, a subsystem or part-system which forms what is known as an artificial antiferromagnet (AAF for short). An AAF part-system of this type is advantageous on account of a relatively high magnetic rigidity and a low coupling with respect to a magnetically softer detection or measurement layer through what is known as the orange peel effect and/or through macroscopic magnetostatic coupling fields.
The structure of corresponding AAF part-systems is fundamentally known (cf. WO 94/15223 A). This system generally comprises at least two ferromagnetic layers, which are antiferromagnetically coupled via a coupling layer made from nonmagnetic material. It may, for example, be formed from two magnetic Co layers and one antiferromagnetic coupling layer of Cu (cf. for example “IEEE Trans. Magn.”, Vol. 32, No. 5, Sep. 1996, pages 4624 to 4626, or Vol. 34, No. 4, Jul. 1998, pages 1336 to 1338, or “Journ. Magn. Magn. Mat.”, Vol. 165, 1997, pages 524 to 528).
To improve the magnetic rigidity of an AAF part-system of this type, that is to say its resistance to external outer magnetic fields, it is known to arrange an antiferromagnetic additional layer on that layer of the part-system which is remote from the detection layer, referred to below as a first ferromagnetic layer. By means of this antiferromagnetic additional layer, the (first) ferromagnetic layer, which is therefore directly adjacent, is additionally pinned in its magnetization on account of the presence of an exchange coupling, so that overall the AAF part-system becomes magnetically harder (known as exchange pinning or exchange biasing).
With a view to limiting the process costs involved in the production of corresponding layer systems and their AAF part-systems, it has hitherto always been assumed that the two ferromagnetic layers of the AAF part-system should consist of the same ferromagnetic material, for example of Co or a Co alloy. In some cases, different layer thicknesses have been planned for these two ferromagnetic layers, in order if appropriate to allow or improve orientation of the magnetization. It has been discovered that this restricts the magnetic matching of the AAF part-system to the remaining parts of the layer system.